Drive for four-wheel driven motor vehicles

ABSTRACT

In a vehicle a drive unit adapted to drive four wheels, the wheels being driven by axle shafts. The drive unit comprises a change speed transmission with its longitudinal axis extending lengthwise to the vehicle longitudinal direction. The drive unit further comprises a transfer gear assembly connected to the output of the transmission and to two transfer shafts which extend parallel to the vehicle longitudinal direction. The drive unit further comprises differential gears driven by the transfer shafts and driving the axle shafts. A housing encloses commonly the change speed transmission, the transfer gear assembly, at least one of the transfer shafts and at least one of the differential gears. The vehicle may be equipped with a starting device attached to the drive unit and employing a brake assembly which may be watercooled.

This application is a continuation-in-part of my prior copendingapplication Ser. No. 190,616 filed Oct. 19, 1971, now abandoned.

BACKGROUND OF INVENTION

The present invention relates to a drive for four-wheel driven motorvehicles such as lorries, buses and tractors.

In four-wheel drives for lorries, buses or tractors having six or morewheels it has so far been usual to equip the four driven wheels withseparate driving axles, the connection between the driving axles and thechange speed transmission being effected via universal-joint shafts.This solution presents the disadvantage that the universal-joint shaftshave to transmit very high torques in the low gear. In vehicles drivenby turbines there arises the additional disadvantage that the overallspeed transformation must be effected substantially in the transmissionrange so that an input or an output transmission must be arranged at theinput or output of the change speed transmission. Until today thevehicles were mainly equipped with friction clutches for startingoperation which have to be actuated by hand, in heavy cars hydraulicallyor pneumatically by means of jaw means.

In order to relieve the driver especially in fast running lorries oromnibuses there is the demand to facilitate the manual operation. Theprovision of hydrodynamic torque converters would meet this demand, butconverters show the known disadvantages in causing a 8 to 10 % loss ofpower. Another proposal was to provide the transmission with brake meanslocated within the oil filled transmission box. But this arangementcauses increased heat dissipation and affords the provision of largefilter means. The present invention eliminates the disadvantages arisingin connection with the used drive constructions and the use of startingclutches.

Accordingly it is the main object of this invention to provide a newdrive for four-wheel driven vehicles employing a new drive unit.

It is further an object of this invention to provide a new compactmounting of the substantial parts of this drive unit so that a commonhousing enclosing all drive unit parts may be provided.

It is further an object of this invention to provide a suspension of thedrive unit on the chassis frame.

A further object of this invention is to equip the drive with a newstarting device replacing the starting clutch usually provided betweenthe engine and the drive input, the starting device employing awatercooled brake.

The foregoing and other objects and advantages will become apparent inview of the following description taken in conjunction with thedrawings, wherein:

FIG. 1 is a vertical cross sectional view taken along the line A -- B ofFIG. 2 illustrating a side view of a drive unit located in the rear partof a heavy lorry,

FIG. 2 is a plan view on the rear part of the lorry of FIG. 1,

FIG. 3 is a vertical cross sectional view illustrating the interior ofthe drive unit of FIG. 1,

FIG. 4 is a cross section view through the transmission taken along theC -- D of FIG. 3,

FIG. 5 is a cross section sectional view taken along the line E -- F ofFIG. 3 illustrating the suspension of a wheel,

FIG. 6 is a vertical cross sectional view through a further embodimentof a drive unit similar to the embodiment of FIGS. 1 to 5, employing adifferent watercooled starting brake and different water-cooled discbrakes,

FIG. 7 is a cross section sectional view taken along the line E -- F ofFIG. 6

FIG. 8 is a schematic longitudinal section view through a driven unitemploying a 10 speed transmission and only one pair of axle shafts beingdriven within the housing,

FIG. 9 is a schematic cross section view through the drive unit of FIG.8,

FIG. 10 is a vertical cross section view taken along the line G -- H ofFIG. 11 of a tractor employing a drive unit according the embodiment ofFIGS. 8 and 9,

FIG. 11 is a vertical longitudinal section view taken along the line J-- K of FIG. 10.

The main principles of the invention are shown in the two embodimentsillustrated in the FIGS. 1 to 5 and in FIGS. 6 and 7. Referring to thesedrawings, the numeral 1 designates the chassis frame of the lorry andthe numerals 2, 3, 4 and 5 designate the four driven wheels. The drivefrom the turbine or the reciprocating engine (not shown) is effected viathe universal-joint shaft 6 which drives the driving wheel 7₁,accommodated in the housing 1₁ of the drive unit 7 of the clutch shiftedchange-speed transmission with the three shafts 7₂, 7₃ and 7₄. Arrangedon the main transmission shaft 7₂ are three twin clutches 7₅, 7₆ and 7₇with corresponding gears 7₈, 7₉, 7₁₀, 7₁₁ and 7₁₂ which continuouslymesh with the intermediate gear rigidly arranged on the auxiliary shafts7₃ and 7₄. Actuation of the rear portion (viewed in the direction oftravel) of the clutch 7₇ transmits the reverse speed via the gear 7₁₂ ;actuation of the front portion of the clutch, the first forward speedvia gear 7₁₁ and actuation of the associated clutches, the second, thirdand fourth forward speed via the gears 7₁₀, 7₉, 7₈ and, finally, closingthe front portion of the clutch 7₅ transmits the fifth direct speed tothe inner sun gear 7₁₃ of the three-component planeting gear assembly.

FIG. 3 illustrates that a brake assembly 8 is provided outwardly of thehousing having a brake housing which is mounted on a shaft portion 7₁₄ 'for rotation. The shaft portion 7₁₄ ' is an axial extension of the ringgear 7₁₄ of the planetary gear extending through an opening of thehousing and being journalled in this opening. The brake assembly acts asa starting and switch device replacing the provision of a starting andswitch clutch usually arranged between the engine and the transmissionunput. When the brake 8 is actuated, the ring gear 7₁₄ is locked and thetorque is translated and transmitted from the sun gear 7₁₃, via theplanet gear 7₁₅ and the axial extension 7₁₆ ' of the planet carrier 7₁₆to the output gear 7₁₇ of the change speed transmission. Thus, powertransmission only occurs when the brake 8 is actuated. For startingapplication the brake 8 is slidingly actuated providing a successivebraking of the planet carrier 7₁₆. It is obvious that also a differentarrangement of the planet components may be provided if useful. Ofcourse, the brake 8 has to be designed appropriately to dissipate theheat arising during the braking operation. A detailed description ofsuch starting devices is in my copending continuation-in-partapplication Ser. No. 349,468, filed Apr. 9, 1973. FIGS. 6 and 7illustrate the employing of a watercooled disc brake in the startingdevice, though other forms of watercooled brake assemblies may beapplied. Referring to this preferred embodiment, FIG. 6 shows that thering gear 7₁₄ has an axial shaft-like extension 7₂₅ on which a linedlamination is mounted for rotation therewith. The linings face on oneside the braking surface of a brake ring 8₆ rigidly fixed with thehousing. The brake ring 8 is provided on its back side with annularchannels 8₇ through which coolant water is passed supplied through theinlet 8₈. On the other side of the lamination an axially movable thrustring 8₁ which can be actuated by the hydraulic means 8₄, 8₅ and 8₉ isprovided.

Returning again to the description of FIG. 3 or FIG. 6, respectively,the transmission output gear 7₁₇ is in mesh engagement with the inputgear 7₁₈ of the transfer gear assembly 7₁₉. It is essential that thetransfer gear assembly is arranged in such a manner in respect to theother parts of the drive unit that its symmetric axis is parallel to thevehicle longitudinal direction, so that the both transfer shafts extendlengthwise in the vehicle. In combination with the neighboring locationof the change speed transmission and the differential gears a newcompact combination is achieved enabling a common housing for all saiddrive unit parts.

In the preferred embodiments the transfer shaft assemblies are arrangedbelow of the transmission driving the two transfer shafts 7₂₀ and 7₂₁which drive the differential gears 7₂₄. Since these two drives areidentical in configuration, only the drive of the pair of wheels 4, 5and finally of the wheel 4 will be described in further detail. Thetransfer shaft 7₂₁ has a bevelled pinion 7₂₂ which drives the gear 7₂₃ ;whence the shafts 13 and 14 are driven via the differential gear 7₂₄ forthe drive of the wheels 4 and 5. Mounted on the shaft 13 is the brakehousing 11₁ of the wheel brake 11 of the wheel 4; the brakes associatedwith the wheels 2, 3 and 5 are designated by 9, 10 and 12. The brakesare preferably located within the housing. In the embodiment of FIG. 6,7 the brakes are designed as watercooled disc brakes. Referring to FIG.7 the brake 11 is as designed as the above described starting brake 8employing a lined rotating lamination, a stationary watercooled brakering and a movable thrust ring.

The housing 1₁ has attached by means of bolts 15 a tubular carrier 16surrounding the axle shafts. Each wheel 2, 3, 4 and 5 surrounds the axleshafts 13, 14, . . . . The wheels 2,3,4,5 are located in a crankcase 17having an eccentric tubular portion 17₃. The crankcases are slewablymounted on the tubular carriers 16₁ by means of the tubular portions 17₃encasing the carriers and of bearings between the carriers and theportions. The axle shafts (13, 14) drive crank gears 13₁, 17₁ located inthe crankcases (17) providing reduced speed of the wheels.

The housing is formed with the brackets 16₁ and 19 and the extensions 20and 21 by means of which the drive unit is elastically suspended on thechassis frame 1 by means of elastic means, for example by means ofrubber thrust bearings 22, 23, 24 and 25. Below these thrust bearings22-25, the brackets engage, via intermediate means 22', 23', 24' and25', respectively, brackets 17₂ integral with and extending out fromcrankcase portions 17₃.

The embodiment just described reveals that the drive unit arranged atthe center between the driving wheels is designed as a unit from whichthe driving wheels are suspended. Of course the wheels also may bemounted on rigid axles and the unit being resiliently supported on therigid axles wherein the wheels are driven via universal-joint shafts.

For vehicles, particularly with a turbine drive which makes a coolingplant unnecessary and would involve a special water cooler for thewater-cooled brakes 8 and 9, 10, 11 and 12 a brake design known as suchmay be adopted for both the starting brake and the wheel brakes having arotating radially ribbed and outwardly open brake housing. Ribbing ofthe brake housings must then suffice on the one hand to dissipate thefrictional heat generated by difficult starting processes and at thewheel brakes in sustained upward-gradient braking as well as consecutivestoppage braking by ventilation on the one hand and on the other, toensure that an excessive loss ventilation effect is created at thehighest speed in use of the vehicle. Most advantageously the five brakesare provided with the same brake-lining segments which can be pulled outof this brake system without dismantling.

In the embodiment schematically illustrated in the FIGS. 8 and 9 thedrive unit comprises a 10 speed countershaft transmission and a modifiedstarting device employing an additional planetary gear. Different fromthe described first embodiment, a transfer shaft extends through theunit housing to a differential gear arranged in the vehicle outwardly ofthe housing. This embodiment therefor may be applied in cases where thedriven wheels are located at a distance in the vehicle. FIGS. 10 and 11illustrate the application of this drive unit in a tractor.

In FIGS. 8 - 11 the reference numeral 27 designates the input gear wheelof the transmission assembly which is directly driven by the engine viathe cardan joint 26, no starting clutch or torque converter beingprovided between the engine and the transmission. The transmission is acombination known per se of a clutch shifted countershaft transmissionwith a planetary gear arranged behind the transmission. The input gear27 meshes with the gear wheels 28 and 29 of the two countershafts andwhich are equipped with further gear wheels 28 through 39 (FIG. 9). Thewheels 30 and 31 mesh with the wheel 40, the wheels 32 and 33 with thewheel 41, the wheels 34 and 35 with the wheel 42, the wheels 36 and 37with the wheel 43 and the wheels 38 and 39 with the gear wheel 46 of themain shaft 47 via the reversing gear wheels 44, 45. Connected with themain shaft 47 are the clutch carriers 48, 49, 50 of the double shiftingclutches 51₁ /51₂ /52₁ /52₂ /53₁ /53₂. The gear wheels and shiftingclutches provide a total of five forward and one reverse speeds. Inorder to double the number of speed ratios a planetary gear unit 54 isprovided of which the ring gear 54₁ is arrested at the first fiveforward speeds by the brakes 54₂ and short-cut by a clutch 54₂ at thefive higher speeds.

The starting device in this embodiment consists of the combination of afurther planetary gear 55 with a water-cooled friction brake 56. Thestarting unit enables power transmission from the transmission outputshaft to the wheels to be discretionally engaged or disengaged. Theplanetary gear 55 together with the tranmission is located in theoil-filled transmission housing while the dry-running friction brake 56,which may be designed as a conical brake, it attached to the housing.The operation of the starting unit is as described in the foregoingembodiment. The transmission output gear 57 is connected to the planetcarrier 55₂ driving the input gear 58 of the transfer gear assembly 59which is located according the foregoing description. Two of the wheelsare driven via the differential gears 60, 61 and the other pair ofwheels are driven via the transfer shaft 78 extending through thehousing and via the cardan joint 62 by the cardan shaft 63.

The truck in which this drive unit may be arranged is equipped with therigid rear, and front axles 65, 66 carrying the wheels 64. The driveunit 70 is suspended on the frame 69. Located above of the drive unit isthe engine 71 which drives the drive unit by means of a chain 72.

On the opposite side of the chain is the radiator assembly comprisingthe fan 73, the radiator clutch 74 and the radiator 76. The foregoingdescribed watercooled starting brake 56 and the watercooled wheel brakes75 which are provided for all wheels are provided with a coolantcirculating system connected to the radiator 76. Located within thewheels are pinion transmissions 67, 68 as shown for a front wheel. AsFIG. 11 illustrates the front wheels are driven by the foregoingmentioned cardan shaft 63.

I claim:
 1. In a vehicle with a chassis frame, a drive unit adapted todrive four wheels, the wheels being driven by axle shafts arrangedtransversely relative to the vehicle longitudinal direction,characterized by the combination of:the drive unit comprising a changespeed transmission with its longitudinal direction extending lengthwiseto the vehicle longitudinal direction, the drive unit further comprisinga transfer gear assembly connected to the output of said transmissionand to two transfer shafts, the transfer gear assembly being arranged inthe vehicle with its transfer shafts extending parallel to the vehiclelongitudinal direction, the drive unit further comprising differentialgear driven by said transfer shafts and driving said axle shafts, ahousing suspended on said chassis frame, said housing commonly enclosingsaid change speed transmission, said transfer gear assembly, at leastone of said transfer shafts and at least one of said differential gears,a starting device between the engine and the drive unit, the startingdevice comprising a brake assembly arranged outwardly of the housing andhaving a rotating member drivingly connected with a member of saidtransmission.
 2. A drive unit according to claim 1, wherein the wheelsbeing attached on rigid axles carrying the said frame.
 3. A drive unitaccording to claim 1, wherein disc brakes are arranged on the axleshafts, the disc brakes being located in said housing.
 4. A drive unitaccording to claim 1, wherein the housing is provided with oppositelyarranged brackets and extensions by means of which the housing iselastically suspended on the frame.
 5. A drive unit according to claim1, wherein the change speed transmission is a combination of a clutchshifted countershaft transmission and a planetary gear, a brake devicebeing provided outwardly of the housing and attached thereto, a rotatingmember of said being in driving connection with a component of saidplanetary gear, the components of the planetary gear and the brakemembers being arranged in respect to one another such that powertransmission from the engine to the driven wheels only occurs duringactuated brake condition providing stationary hold of said component andsuch that starting occurs during sliding actuation of the brakeproviding successive braking of said component, thus replacing the useand the provision of the normally used starting clutch between theengine and the transmission unit.
 6. A drive unit according to claim 1,wherein the change speed transmission is a combination of a clutchshifted countershaft transmission and a planetary gear, saidtransmission member being a component of said planetary gear, thecomponents of the planetary gear and the brake members being arranged inrespect to one another such that power transmission from the engine tothe driven wheels only occurs during actuated brake condition providingstationary hold of said component and such that starting occurs duringsliding actuation of the brake providing sucessive braking of saidcomponent, thus replacing the use and the provision of a normally usedstarting clutch between the engine and the transmission unit.
 7. A driveunit according to claim 1,said change speed transmission being acombination of a clutch shifted countershaft transmission with aplanetary gear assembly, said starting device comprising a planetarygear having several components and being located within said housing, afirst of said components being drivingly connected with said rotatingmember of said watercooled brake, and a second of said components beingdrivingly engaged with said transfer gear assembly, said components andsaid brake members being arranged in respect to one another that powertransmission only occurs when said brake is in actuated condition.
 8. Adrive unit according to claim 1,said vehicle being a tractor equippedwith a rear rigid axle carrying the rear wheels and with a front rigidaxle carrying the front wheels, said housing being suspended on saidrigid axles, and the drive unit being located in the rear part of saidtractor, said change speed transmission being a combination of a clutchshifted countershaft transmission with a planetary gear assembly, saidstarting device comprising a planetary gear having several componentsand being located within said housing, a first of said components beingdrivingly connected with said rotating member of said watercooled brake,and a second of said components being drivingly engaged with saidtransfer gear assembly, said components and said brake members beingsuch arranged in respect to one another that power transmission onlyoccurs when said brake is in actuated condition, said transfer gearassembly being located below said change speed transmission, thetransfer shaft extending through said housing and driving by means of acardan joint a cardan shaft driving the front axle shafts, watercooleddisc brakes being located on each axle shaft and within said housing,the truck engine being equipped with a radiator providing a coolantwater circulation through said brake of said starting device and throughsaid disc brakes.
 9. A drive unit according to claim 1, wherein thehousing is provided with tubular carriers surrounding said axle shafts,the wheels being located in crankcases, each of which have an eccentrictubular portion, said crankcases being slewably mounted on said tubularcarriers by means of said tubular portions encasing said carriers and ofbearings between said carriers and said portions, said axle shaft drivecrank gears being located in the crankcases providing reduced speed ofthe wheels.
 10. A drive unit according to claim 1, whereinthe changespeed transmission is a combination of a clutch shifted countershifttransmission and a planetary gear, the planetary gear comprising adriven sun gear, a ring gear, a planetary carrier carrying planetarygears meshing with said sun and ring gears, an axial extension of theplanetary carrier having attached thereon the change speed transmissionoutput gear, said output gear meshing with the input gear of saidtransfer gear device, the transfer gear device being located below thechange speed transmission, a shaft connected with said ring gearextending through an opening of said housing and means for journallingsaid shaft in said opening, said rotating brake member being a linedlamination mounted on said shaft for rotation therewith, said brakeassembly further comprising a brake ring mounted in the housing andprovided with waterflow channels, an axially movable thrust ring andactuating means to move said thrust ring towards said lamination untilfriction contact, said brake assembly holding said ring gear fixedduring actuation thus enabling power transmission from being designedowing to its cooling for sliding actuation thus acting as startingdevice replacing the provision of a normally used starting clutch, saidtransfer shafts and said differential gears being arranged within saidhousing, said housing being formed with two oppositely arranged bracketsand two extensions provided with elastic bearings by means of whichbrackets, extensions and bearings the housing is suspended on thechassis frame, each said disc brake comprising a brake housing mountedon said axle shifts for rotation therewith providing an annularperipheral open space and said brakes further comprising a stationaryspreading device extending into said annular space, said disc brakesbeing arranged within said housing, said housing being provided withtubular carriers surrounding said axle shafts, the wheels being locatedin crankcases, each having an eccentric tubular portion, said crankcasesbeing slewably mounted on said tubular carrier by means of said tubularportions encasing said carriers and of bearings between said carriersand said portions, said axle shafts drive crank gears located in thecrancases providing reduced speed of the wheels.
 11. A drive unitaccording to claim 1, said brake assembly of the starting device being awatercooled brake assembly.
 12. A drive unit according to claim 1,including disc brakes arranged on said axle shafts to brace therespective wheels.
 13. A device unit according to claim 12, said discbrakes being watercooled disc brakes.